First, the crf file is a combined .ash (track shape) and audio (mp3/ogg/wma/whatever) file. The ASWT will extract the two parts when you point it at the file.
The download link for the crf is in the news page on the left hand side of the ASWT application (it's the megaupload link or it's mirrored by lavacano if you don't want to use megaupload), scroll down to see it.
You don't have to buy it, although if you like the music (there's more to listen to on the band's website) then I would say bands contributing to the tournament are worth supporting.
There's now detailed instructions for how to use the app in the add-ons section post that should answer the rest of your questions:
http://www.audio-surf.com/forum/index.php/topic,6728.0.html